Anatonn'caf Nomenclature of Echt'noderms. 



19 



Illustrative Formulce. 



ntedon th-ynuA A. R. .'}. 2. (2) - 



r 



— incciunlis V. 3. -^/'^- '"' .^L 



•2 h 



— porrecta V. 3. 2 | (»). hr \ . ~ 



ztiiwmetra Solaris .... a. II. . _. 

 2 ab 



T^ d. (p). hr /r/\ 



— pnuctcirra a. u. — >-'^^ . / 1 



— midtihrachiata . . a. R. 3. P- >>'■■■■ P'' ^"- . * 



2 a 



— MUyera a. 2. 2. (2). -^' . ^\ 



2 CO 



boeoino.a A. ^ . 3. 2. (2) . -t 



- y 



A. 3. 2 {(;;). /.[.^/. 



c. b xii 



a. -^ 1. 



2 xy 



c. d. (p). h /.v\ 

 2 U/" 



a.'L.ii P-p'----p''^ y. 



"2 2 -x 



„ «.2.2.(2).J..V5. 



2 xy 



5. J7<e use of the term "Axillart/.^^ 



The term " axillary " was introduced by Miiller * and de- 

 fined as follows : — " Das dritte radiale hat nach oben zwei 

 dachformig geneigte Gelenkfliichen fiir die beiden darauf 

 sitzenden Arme. Icli nenne es deswegen radiale axillare^ es 

 ist Miller's Scapula, dagegen nenne icli hrachialia axillaria 

 alle im Verlauf der Arme vorkonimenden ahnlichen Glieder, 

 auf dcnen zwei Theilungsarme aufsitzen." 



The terra has been generally used in tlie Miillerian sense 

 during the last forty years, i. e. only with reference to plates 

 which serve as points of division in the rays and arms, 

 whether these be free or incorporated into the more or less 

 rigid dorsal cup. Bather, however, has recently extended its 

 use in a manner which is scarcely advisable at present, since 

 it is not as yet justified by anatomical research. He has 

 applied the name to tlie " bifurcating piece " in locrinus which 

 gives rise both to the right posterior ray and to the ventral 

 sac t. The lowest of the series of plates supporting the ven- 

 tral sac — that which rests on the left upper edge of the bifur- 

 cating ])iece, and is marked x in Bather's diagram \ — is 

 regarded by him as having " originated as a plate morpho- 

 logically corresponding to an ordinary brachial ; " and he 



* " Ueber den JJau des Pentacrinus caput Medusts^' Abliandl. Berlin. 

 Akad. 1841 [1843], p. 202. 



t Ann. & Mag. Nat. Hist. .ser. G, vol. v. 1890, p. 320. 

 X Ibid. pi. xiv. fig. o. 



2* 



